This work was supported by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) grants F31-DK-113673 (C.L.F.), T32-GM-095421 (C.L.F.), DK-089056 (G.J.M.), an American Diabetes Association Innovative Basic Science Award (#1-19-IBS-192 to G.J.M.) and the NIDDK-funded Nutrition Obesity Research Center (DK-035816), Diabetes Research Center (DK-017047) and Diabetes, Obesity and Metabolism Training Grant T32 DK0007247 (T.H.M) at the University of Washington.

All procedures were approved in accordance with the National Institutes of Health, the Guide for the Care and Use of Animals and were approved by both the Institutional Animal Care and Use Committee (IACUC) and Environmental Health and Safety at the University of Washington.
1. Calculation of angled coordinates
<ol>
	<li>Using a coronal brain atlas, mark a right triangle so that the hypotenuse passes through the target region of interest. In the representative example (F...

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Recent advances in neuroscience have supported advanced insight and understanding into the activity and function of brain neurocircuits. This includes the application of optogenetic and chemogenetic technologies to activate or silence discrete neuronal populations and their projection sites in vivo. More recently, this has included the development of genetically encoded calcium indicators (e.g., GCaMP, RCaMP) and other fluorometric biosensors (e.g., dopamine, norepinephrine) for in vivo recording of neuronal activity in ...

Neural control of behavior, feeding, and metabolism involves coordination of highly complex, integrative, and redundant neurocircuits. A driving goal of the neuroscience field is to dissect the relationship between neuronal circuit structure and function. Although classical neuroscience tools (i.e., lesioning, local pharmacological injections, and electrical stimulation) have uncovered vital knowledge regarding the role of specific brain regions that control behavior and metabolism, these tools are limited by their lack of specificity and reversibility1.
Recent advances in the neuroscience field have greatly improved the ability to interrogate and manipulate circuit function in a cell-type specific manner with high spatiotemporal resolution. Optogenetic2 and chemogenetic3 approaches, for instance, allow the rapid and reversible manipulation of activity in genetically defined cell types of freely moving animals. Optogenetics involves the use of light-sensitive ion channels, termed channelrhodopsins, to control neuronal activity. Key to this technique is the gene delivery of channelrhodopsin and a source of light to activate the opsin. A common strategy for gene delivery is through a combination of 1) genetically engineered mice expressing Cre-recombinase in discrete neurons, and 2) Cre-dependent viral vectors encoding channelrhodopsin.
While optogenetics provides an elegant, highly precise means to control neuronal activity, the method is contingent upon successful stereotactic microinjection of the viral vector and fiberoptic placement into a defined brain region. Although stereotactic procedures are commonplace within the modern neuroscience lab (and there are several excellent protocols describing this procedure)4,5,6, being able to consistently and reproducibly target discrete brain regions along the midline (i.e., the mediobasal hypothalamus, a brain area critical to the regulation of homeostatic functions7) presents additional challenges. These challenges include avoiding of the superior sagittal sinus, third ventricle, and adjacent hypothalamic nuclei. In addition, there are significant spatial limitations to the bilateral implantation of hardware that is required for inhibition studies. With these challenges in mind, this protocol herein presents a modifiable procedure for targeting discrete brain regions via an angled stereotactic approach.

<table>
	<tbody>
		<tr>
			<td>Fiberoptic Cannulae</td>
			<td>Doric Lenses</td>
			<td>MFC_200/230-0.57_###_MF1.25_FLT</td>
			<td>Customizable</td>
		</tr>
		<tr>
			<td>Kopf Model 1900 Stereotaxic Alignment System</td>
			<td>Kopf</td>
			<td>Model 1900</td>
			<td></td>
		</tr>
		<tr>
			<td>Kopf Model 1900-51 Center Height Gauge</td>
			<td>Kopf</td>
			<td>Model 1900-51</td>
			<td></td>
		</tr>
		<tr>
			<td>Kopf Model 1905 Alignment Indicator</td>
			<td>Kopf</td>
			<td>Model 1905</td>
			<td></td>
		</tr>
		<tr>
			<td>Kopf Model 1911 Stereotaxic Drill</td>
			<td>Kopf</td>
			<td>Model 1911</td>
			<td></td>
		</tr>
		<tr>
			<td>Kopf Model 1915 Centering Scope</td>
			<td>Kopf</td>
			<td>Model 1915</td>
			<td></td>
		</tr>
		<tr>
			<td>Kopf Model 1922 60-Degree Non-Rupture Ear Bars</td>
			<td>Kopf</td>
			<td>Model 1922</td>
			<td></td>
		</tr>
		<tr>
			<td>Kopf Model 1923-B Mouse Gas Anesthesia Head Holder</td>
			<td>Kopf</td>
			<td>Model 1923-B</td>
			<td></td>
		</tr>
		<tr>
			<td>Kopf Model 1940 Micro Manipulator</td>
			<td>Kopf</td>
			<td>Model 1940</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro4 Microinjection System</td>
			<td>World Precision Instruments</td>
			<td>--</td>
			<td></td>
		</tr>
		<tr>
			<td>Mouse bone screws</td>
			<td>Plastics One</td>
			<td>00-96 X 1/16</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereotaxic Cannula Holder, 1.25mm ferrule</td>
			<td>Thor Labs</td>
			<td>XCL</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical Drill</td>
			<td>Cell Point Scientific</td>
			<td>Ideal Micro Drill</td>
			<td></td>
		</tr>
	</tbody>
</table>

adaptable angled stereotactic approach for versatile neuroscience techniques

Stereotactic surgery is an essential tool in the modern neuroscience lab. However, the ability to precisely and accurately target difficult-to-reach brain regions still presents a challenge, particularly when targeting brain structures along the midline. These challenges include avoiding of the superior sagittal sinus and third ventricle and the ability to consistently target selective and discrete brain nuclei. In addition, more advanced neuroscience techniques (e.g., optogenetics, fiber photometry, and two-photon imaging) rely on targeted implantation of significant hardware to the brain, and spatial limitations are a common hindrance. Presented here is a modifiable protocol for stereotactic targeting of rodent brain structures using an angled coronal approach. It can be adapted to 1) mouse or rat models, 2) various neuroscience techniques, and 3) multiple brain regions. As a representative example, it includes the calculation of stereotactic coordinates for targeting of the mouse hypothalamic ventromedial nucleus (VMN) for an optogenetic inhibition experiment. This procedure begins with the bilateral microinjection of an adeno-associated virus (AAV) encoding a light-sensitive chloride channel (SwiChR++) to a Cre-dependent mouse model, followed by the angled bilateral implantation of fiberoptic cannulae. Using this approach, findings show that activation of a subset of VMN neurons is required for intact glucose counterregulatory responses to insulin-induced hypoglycemia.

This protocol describes a surgical procedure for performing optogenetics studies to interrogate the role of hypothalamic VMN neurons in glycemic control9. First utilized was a standard (non-angled) stereotactic approach for the bilateral microinjection of an inhibitory channelrhodopsin virus to the VMN. While an angled approach would also be suitable, the standard (non-angled) approach was selected because it is sufficient to target the brain region of interest and is an easy, reliable and consist...

Watch this Scientific Journal Video about Adaptable Angled Stereotactic Approach for Versatile Neuroscience Techniques at JoVE.com

Adaptable Angled Stereotactic Approach for Versatile Neuroscience Techniques

Described here is a stereotactic procedure that can target challenging and difficult-to-reach brain regions (due to spatial limitations) using an angled coronal approach. This protocol is adaptable to both mouse and rat models and can be applied to diverse neuroscientific applications, including cannula implantation and microinjections of viral constructs.

Stereotactic surgery is an essential tool in the modern neuroscience lab. However, the ability to precisely and accurately target difficult-to-reach brain ...

This protocol is significant as it is an adaptable, stereotactic procedure that can be utilized in both mice and rats, and can be applied to many new neuroscientific techniques. The main advantage of this adaptable stereotactic procedure is it's ability to be used to target challenging and difficult-to-reach regions of the brain. Demonstrating the procedure will be Chelsea Faber, a young, talented post-doctoral research fellow in the laboratory.After confirming that the frame and micromanipulator have been calibrated, place the center height gauge into the socket of the head holder baseplate. Secure the centering scope in the tool holder and sight down the scope. Adjust the position of the micromanipulator until the crosshairs are aligned and focused on the gauge crosshairs, and place the ear bars into the holders such that the indicator lines on both sides are at zero.Use the medial-lateral and anterior-posterior knobs on the head holder to centerline the ear bars in the X and Y planes above the crosshair of the center height gauge. To align the ear bar position in the Z-axis, remove the ear bars from the holder and remove the center height gauge. Then, replace the ear bars and re-center the bars at zero.Then, sight down the scope again, and use the vertical shift and coronal tilt knobs respectively to lower and rotate the ear bars until the scope crosshairs remain centered between the ear bars throughout coronal rotation. To align the central axis of rotation for angled coordinates, secure the centering scope in the tool holder and position the micromanipulator to the calculated coordinate. Note that the right/left coordinate for the angled implantation corresponds to the length of side A.Sighting down the scope, mark this coordinate to represent the point at which the cannula will enter the brain, once the head is rotated.Reposition the micromanipulator over the midline, and use the coronal tilt knob to rotate the head to the calculated angle. If the scope crosshairs do not line up with the reference mark, use the vertical shift knob to adjust the head position in the Z-axis until the crosshairs line up as close as possible to the mark. At this point, the arbitrary point of rotation should be aligned with the center of rotation of the stereotax.Rotate the head back to the zero degree coronal position before proceeding to subsequent drilling and microinjection steps. After performing the microinjection, return the head to the zero degree level position, and use a hand drill to place two holes, anteriorly, and two holes, posteriorly, far enough from the angled coordinate burr holes to accommodate the ferrule portion of the fiberoptic that sits above the skull. When all of the holes have been drilled, use a small flathead screwdriver to insert the bone screws as gently as possible, such that they sit firmly in the skull without penetrating the brain.Clamp a fiberoptic cannula into the cannula holder, and place the cannula holder in the tool holder. Rotate the head to the calculated angle, noting that the coordinates of the micromanipulator do not apply to the new tool. Use the center of the angled burr holes as the implantation target.Lower the fiber optic until it just touches the dura within the center of the burr hole, and zero the micromanipulator in the Z-axis. Slowly lower the fiberoptic to the dorsal ventral angled coordinate, then use cyanoacrylate gel to connect the fiber optic ferrule to the ipsilateral anchor screws. Use a micropipette tip to apply an accelerant.Once the gel has completely hardened, gently loosen and raise the cannula holder until it is clear of the ferrule. Implant the second fiberoptic to the contralateral angled coordinate, then level the head. For extra security, use the cyanoacrylate gel and accelerant to make an additional connection between the two angled fiberoptic cannulas, and apply a small, relatively thin amount of dental cement to the surface of the skull, taking care to thoroughly cover the anchor screws and the base of the fiberoptic cannulas.To interrogate the role of hypothalamus ventromedial nucleus neurons in glycemic control, in this representative analysis, a standard, non-angled, stereotactic approach was utilized for the bilateral microinjection of an inhibitory channel rhodopsin virus to the ventromedial nucleus. Given the proximity of the ventromedial nucleus to the midline, space constraints did not permit a non-angled implantation of bilateral fiberoptics, necessitating the development of a surgical strategy for precisely implanting fiberoptics at an angle. The most important things to remember are to simply be patient and to take your time, as being consistent and accurate with your coordinate assignments is critical to success.This procedure can be adapted and applied to any neuroscientific method requiring microinjection or implantation into the rodent brain, including chemogenetics, optogenetics, and fiber photometry approaches.

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4.7K visualizações.  University of Washington. This protocol is significant as it is an adaptable, stereotactic procedure that can be utilized in both mice and rats, and can be applied to many new neuroscientific techniques. The main advantage of this adaptable stereotactic procedure is it's ability to be used to target challenging and difficult-to-reach regions of the brain. Demonstrating the procedure will be Chelsea Faber, a young, talented post-doctoral research fellow in the laboratory.After confirming that the frame and micro...